AM in Phoenix is probably the best dance floor in the Phoenix area that is available to the public. The suspended wood floor is well maintained and it's big enough for large events. There is a smaller floor in a separate room for private lessons.
The location is kind of weird until you get used to it. The neighborhood isn't the best but fortunately the parking lot is in the back of the building and seems safe.
The ballroom has a good sound system although the music they play often isn't the best. Air conditioning in the summer can be hot enough to be uncomfortable.
I can't vouch for the AM studio or the lessons because I haven't tried any there. I often go there for the Sunday Desert City Swing, which is a wonderful West Coast Swing event, and for the USA Dancesport ballroom party that is held there once every other month.
For more info about USA Dance go to:
http://phoenixusadance.org/